I'm working for a small non-profit that builds houses for families well below the poverty line, and we have zero assets. I'm trying to get an original 20" iMac G5 1.8 GHz running 10.3.5 to work properly again or else it probably goes on ebay "as-is." Symptoms: Was working well then would randomly shut down, but was usable. Now, after trying the following it shuts down after only a few seconds! But occasionally will stay up for a few minutes or more. What I tried: Firstly, I ran a hardware diagnostic on Install Disk 3; everything passed. Then I did a clean install and wrote zeros to the HD using the original install disks. Even booted from the CD, it randomly shut down. Obviously a hardware issue. I then tried the standard PRAM and NVRAM reset, no luck. Then I took the back off and did the SMU reset and startup from the internal power button and held it until I heard the loud "beep." I also tried taking out the clock battery for 10 min and the airport extreme card. According to the 4 internal leds, the PMU is fine. I also switched the RAM to another slot. After multiple random shutdowns during startup from both the CD and HD, I would again do the SMU & PRAM reset. No externals are attached. Does anyone have any ideas besides replacing the power supply and/or logic board? We really can't afford to go that route... Thanks so much!